Solar cell Fabrication Based on Surface
Modified PbS Colloidal Quantum Dots
Abstract of Master’s Thesis, 2017
Solar cell Fabrication Based on Surface Modified PbS
Colloidal Quantum Dots
Graduate School of Science and Technology, Kwansei Gakuin University
1
Department of Chemistry,
2Masuo Lab, Luis Fernando Galo
Lead sulfide (PbS) colloidal quantum dots (CQDs) have great potential due to their high efficiency, low-cost, high stability, bandgap tunability, and multiple exciton generation (MEG). Recently, the efficiency of CQD devices has increased drastically due to CQD surface chemistry modification. Modern devices have achieved efficiencies close to 11% owing to the fact that iodide doping can help to improve surface passivation, decrease of trap states, and bandgap engineering. Another path commonly used to increase the efficiency of solar cells is the device architecture, this works by employing layers of QDs treated with different ligands to tune the relative band alignment. This work focused on increasing the performance of PbS QD solar cells by adding an electron-blocking/hole-extraction layer. The device architecture of the solar cells is comprised of an indium tin oxide (ITO) substrate, zinc oxide (ZnO) layer, methylammonium iodide (MAI) treated PbS QDs followed by inorganic ligand passivation using tetrabutylammonium iodide (TBAI), followed by a layer of PbS QDs passivated by 1 2 ethanedithiol (EDT), finished with a gold anode. As previously stated, the addition of the EDT passivated PbS QDs layer served the purpose of an electron-blocking/hole-extraction layer this is because this additional layer prevents a direct path to electrons to flow from the 𝑃𝑏𝑆𝑀𝐴𝐼 -TBAI layer to the anode therefore reducing charge recombination. The, devices performance were evaluated by electrical characterizations under AM1.5G irradiation (100 mWcm-2). The devices with the extra electron-blocking/hole-extraction layer obtained a photo conversion efficiency (PCE) of 5.34%, the devices without the extra layer obtained a PCE of 3.22%.
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